Bearing alloy



. Patented Nov. 15 1938.

UNITED E A NT m i I 2,130,655' w L i F Julian G. Ryaffifiiifiik assign Shell Development Company, San Francisco, Oalifi, a corporation of Delaware gines.

. No Drawing. j Original a plicationnctober 18,

1937. Serial No. 169,645. Divided and this application March 26,1938; SerialNoL 198,271

3- Claims. (01. raj- 151) I This invention is chiefly concerned with hear-.- ing compositionsusedin internal combustion en It. has been recognized. that bearings should-comprise at least. two constituent parts, namely, a soft part to, conform to the crankshaft and readjust itself to irregularities in operation and-a hard part to support the load and have found in tin base bearing alloys' comm'only known as babbitt. l This application is a division of my application Serial No. 169,645 filed October 18, 1937'.

In recent years owing to the greater speeds re- 'quired of automotive engines, the higher oillteme peraturesproduced have caused a softening of the babbitt and in some cases, actual melting due to the eutectic melting'pointbe'ing around the softening point being around 212 F. e p t Endeavor has therefore ben'made to develop bearing metals, which would have anti-friction properties-and have a high enough melting point that the softeningftemperature wouldbe raised above that of the tin base bearings and at the same time be economical. I

' Two'of the bearing materials which have been produced to meet this requirement :are cadmium? silver and cadmium-silver-copper compositions.

Cadmium is the main constituent bf these compositions. Cadmium has a 'melting' point of about 650 F. and a Brinell hardness of over-20. Furthermore cadmium has good bonding properties as evidenced by its high strength solders.

Silver, when added to the cadmium in relatively small quantities, improves the casting qualities of cadmium by making it less susceptible to oxidation at casting temperatures and by increasing the fluidity. Silver, further, has a marked infiuence upon the physical characteristics of cadmium by improving grain structure.

A- typical cadmium silver bearing. alloy will have the following composition: cadmium 97.75%

and silver 2.25%

,the silver beingheldin solution composition has the property of'raising the Brinnell hardness appreciably. A typical cadmiumv silver-copper composition is as follows: cadmium 98.75%, silver 0.75% and copper 0.50%.

These bearings have, in general, been quite successful. However, in manycases', corrosion of the hearing has taken place, Many theories have been advanced to explainthis, and various oil successful use. with zinc in electrolyte.

that one of-the main causes of becomingcorro sive can be traced to the composition of theibear-" ing alloys-and it'is the object ofthisinvention to provide substantially anti-frictionalqualities in order not to seize onto the shaft. These properties have in the past been on-corrosive internal combustion e nes. 1 I have-found. that the corrosion is inpart :due to galvanic action betwee the constituents of the bearing material submerg d inmineral or,hydro-' carbon oil. This galvanic action takes .place bearings for through the intermediary .of the lubricating oil.

The electrical conductivity of the 'oil is veryslight under normal circumstances, but upon oxidation of the lubricant andftheaccumulation of, small the conductivity is materially increased.

According to my investigation, I have found that in some cases the 'cadmium silver bearings amounts of water in the crankcase of the motorafter being run in anautomobile motor for several hours showed pitting of the bearings. Subsequent analysis {of the oil failed to show any cadmium particles in the oil, thus eliminating abrasion of the metal or insufficient oiliness of the oil-as the cause of corrosion. This led to the. conclusion that at least part of the corrosion wasx due to electrochemical action. This conclusion was further-supported by the fact that only the cadmium went into solution and silverwas not. found dissolved in oil in conformity with its lower position in; theelectromotive series. Further ex'- p'e'riments were then conducted to establish the electrode potentials between. cadmium and silver electrpdes placed in a used motor lubricating oil '.bath. Measured at an oil temperature of 210 F. a potential of .630 voltwas established. In

order-to investigate the eifect of electrolyte further, small buttons of polished cadmium with pure silver inserts were exposed to oils under a variety of test conditions. The polished surfacewas examined under a microscope before and after the tests. The results of these tests showed that cadmium corrodes easily and that galvanic action accelerates'the corrosion. The silver in-.

serts were not attacked. A series of tests with numerous alloyshave, established that there exists a direct relationship between the rate of corro- I have found that by alloying a small quantity "oi v apotential depressing substance with the bearing material corrosion may be prevented or at least substantially reduced. Of various sub stances tested in alloys with the cadmium-silver and cadmium-silver-copper bearings I have found that antimony is particularly efiective for the purpose desired.

Below are tabulated the results obtained usin an oil electrolyte at 340 F.

Equilibrium potential millivolts Composition of cathode Composition of anode Cadmium Cadmium-+0. 2% antimony by wt.-. Cadmium-+2. antimony by wt... Cadmium+5. 0% antimony by wt...

the result that the cadmium-antimony electrodes w after an hour, had a very fine grained finish and showed only slight corrosion. Microscopic examination showed that'the crystal structure of the metal was changed by the presence of the antimony. This isv probably also a factor'in reducing corrosion.

. Further tests were made, using a silver cathode and an anode of standard cadmium-silvercopper bearing metal and anodes of the same with small amounts of antimony added. The results of these tests are tabulated below using the same oil at 340 F.

g gfi gg Composition of anode potential miliivolts Commercial cadminm-sllver-coppen 525 Commercial cadmium-silver-oopper +0.1% antimony by weight.

Commercial cadmium-silver-copper +02% antimony by weight- To obtain further information regarding the addition of antimony to bearing alloys the following test was made: Small pieces of the same material as was used for the anodes in the above test were machined into the form of cylindrical slugs weighing 8 grams each, carefully polished and washed with solvent. Each specimen was then placed in a test tube containing a measured amount of a used lubricating oil. The test tubes and contents were each kept at a temperature of 340 F., air was continually bubbled through the oil to simulate actual operating conditions. At the end of a period of sixteen hours the slugs were removed and after careful washing and. drying, were weighed. The results are shown below:

l Number of Average Alloy specimens loss Mgs. 1. Commercial cadmium-silver cop is 9 24 2. (1)+0.l% antimony l3 3. (Di- 0.2% antimony 5 7 place the copper with antimony which will serve both to harden the alloy and reduce corrosion.

While I have shown only tests using specific amounts of antimony, the conclusion must be drawn that amounts between the examples will be beneficial for the purpose intended and that I do not intend to limit myself to the exact proportions given.

I claim as my invention:

1. A hearing metal consisting of silver 0.5% to 1%, copper 0.25% to 0.75%, antimony 0.1% to 1% and the remainder cadmium.

2. A bearing metal consisting of silver 0.5%

-to 1%, copper 0.25% to 0.75%, antimony 0.1%

to 0.2% and the remainder cadmium.

3. A hearing metal consisting of silver 0.5% to 1%, copper 0.25% to 0.75%, antimony 0.1% and the remainder cadmium.

JULIAN G. RYAN. 

